Linking geometry to failure: utilizing lattice structures to tailor the failure mode of soft gels

Hydrogels are hydrophilic polymer networks that are utilized heavily in biomedical fields and other soft matter applications, due to their high degree of tunability and biocompatibility. Despite the widespread interest in this material platform, a significant challenge to using hydrogels in applications is their limited mechanical performance, e.g., lack of toughness, catastrophic failure. Motivated by prior demonstrations that perforated and/or lattice structures can be leveraged to manipulate the failure mode of materials, here we experimentally investigate the relationship between failure mode and patterning in poly(ethylene glycol) (PEG)-based hydrogels. By varying the aspect ratio of the imposed lattice pattern, as well as the rigidity of the PEG network (as manipulated by network cross-link density), we observe a transition in failure mode, e.g., from catastrophic to slow and diffuse failure. Furthermore, we also highlight our ongoing work leveraging the photoelastic properties of these hydrogels to understand how stress fields develop just prior to observed failure.